Empty matrix

[george brida]

Dear Octavers,
I programmed a function 'matrix_exp' that returns a matrix x with dimension (T-m, 2*p+8), where T, m and p are known number. The problem when I call this function to return this matrix, I obtain from Matlab this message:"empty matrix 0 by 16", I choose p=4. Nevertheless when I repeat the lines that defined this function in another program, I obtained this matrix (i.e without any call of this function). So, I conclude that the lines I written to define the function 'matrix_exp' are true but I don't understand the message of Matlab.
Can you please help, thank you in advance.
George